Can I use this calculator for a child under 2 years old?

No, the NHS tool is designed for children and teenagers aged 2 to 17. For children under 2, you should speak to a GP or health visitor about growth assessment.

Does the calculator provide a body fat percentage?

No, this BMI calculator does not give a body fat percentage or tell the difference between muscle and fat; it only provides a BMI centile based on growth chart data.

What should I do if the BMI result shows a concern?

The tool includes advice on what to do next; if you are worried about a child's weight or growth, contact the child's health visitor, school nurse, or GP surgery for professional guidance.

Is this calculator suitable for pregnant teenagers?

No, the calculator specifies that it should not be used for people who are pregnant; separate BMI calculations apply for adults and pregnancy.

Body Metrics & FitnessTool Review

BMI Calculator for Kids

Provided byNHSnhs.uk

This free NHS calculator checks BMI for children and teenagers aged 2 to 17, covering both girls and boys including a...

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About this tool

What BMI Calculator for Kids does

This free NHS calculator checks BMI for children and teenagers aged 2 to 17, covering both girls and boys including age 9. It uses child-specific inputs such as date of birth, sex at birth, height, and weight to provide guidance. The page also explains who should use the tool and limitations of BMI interpretation. Results compare the child’s measurements to national growth charts, producing a BMI centile and category rather than a single number. The tool is designed for use with a parent or carer if the user is aged 17 or under, and it includes clear advice on next steps if concerns arise. The interface walks the user through each required field with plain-language prompts and references official RCPCH growth chart data sources, offering a level of clinical context uncommon in generic calculators.

Step by step

How to use the NHS BMI Calculator for Kids

1
Enter the child's date of birth to determine age eligibility
2
Select the child's sex at birth from the available options
3
Input the child's current height and weight measurements
4
Specify when the measurements were taken to ensure accuracy

Is it right for you

Best for

Parents, carers, or guardians in the UK who need a quick, free way to assess a child's weight status against age- and sex-specific growth charts.

Limitations

Results are based on BMI centiles and do not distinguish between muscle and fat
The tool does not account for the child's ethnic background or physical activity levels
BMI is an estimate and should not be used to diagnose medical conditions

Questions

BMI Calculator for Kids FAQ

Can I use this calculator for a child under 2 years old?: No, the NHS tool is designed for children and teenagers aged 2 to 17. For children under 2, you should speak to a GP or health visitor about growth assessment.
Does the calculator provide a body fat percentage?: No, this BMI calculator does not give a body fat percentage or tell the difference between muscle and fat; it only provides a BMI centile based on growth chart data.
What should I do if the BMI result shows a concern?: The tool includes advice on what to do next; if you are worried about a child's weight or growth, contact the child's health visitor, school nurse, or GP surgery for professional guidance.
Is this calculator suitable for pregnant teenagers?: No, the calculator specifies that it should not be used for people who are pregnant; separate BMI calculations apply for adults and pregnancy.

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